Mechanistic Performance of Modified Carbon Nanotubes Stabilized in Water-Based Drilling Fluids for High-Temperature Applications

Abstract

Utilization of water-based drilling fluids (DFs) at high temperatures is limited by multiple factors due to the degradation of the rheological and filtration properties. Therefore, it is imperative to design a thermally resilient system that can overcome these limitations. Carbon nanotubes (CNTs), renowned for their exceptional mechanical, thermal, and electrical properties, emerge as promising additives for maintaining the performance of DFs at elevated pressure–temperature conditions. However, CNTs have limited dispersibility in water, thereby reducing their efficacy. This experimental investigation aims to comprehensively evaluate the efficacy of modified CNTs in DFs under high-temperature conditions. The surface modification was performed by wet-base oxidation after which the modified CNTs (mMWCNTs) were further stabilized in a polymeric dispersion at 9 pH. The study employs a systematic approach encompassing material characterization, rheological analysis, stability assessments, and filtration performance evaluations at 500 psi pressure and different temperatures (20 and 80 °C) both before and after aging at simulated high-temperature environments (150 °C). The filtration losses were reduced by 55% while the rheological profile displayed over 40% improvement in comparison to the base samples. The mMWCNT could improve the viscosity retention of the DF by 52% at an elevated temperature–pressure condition. Moreover, the study scrutinizes the viscoelastic behavior of the mud where the yield properties were enhanced from the strain rate of 4.5% (in base DF) to 70% (mMWCNT infused DF), validating the microstructural robustness imparted by the modified nanotubes. Findings from this experimental investigation not only contribute to a deeper understanding of the synergistic interactions between modified CNTs and water-based DFs but also offer valuable insights into their practical applicability for high-temperature drilling operations.